UIAlertView-Show red if data not entered - iphone

Question

I have a save button, which on click shows an alert box.I want the user to enter some data in the box and if he/she does not enter any data and press ok I want to make the alert box text field red i.e indicating its mandatory.For the moment I am showing another alert box.Please help me,Thanks.
following is the code.
-(void) saveCalculaterData{
UIAlertView *prompt = [[UIAlertView alloc] initWithTitle:REFERENCE_ID
message:#"\n\n"
delegate:self
cancelButtonTitle:#"Cancel"
otherButtonTitles:#"OK", nil];
textField = [[UITextField alloc] initWithFrame:CGRectMake(12, 50, 260, 25)];
textField.tag=REFERENCE_FIELD;
[textField setBackgroundColor:[UIColor whiteColor]];
[textField setPlaceholder:ADD_REFERENCE_ID];
[prompt addSubview:textField];
[prompt show];
[textField becomeFirstResponder];
textField.delegate=self;
}
- (void)alertView:(UIAlertView *)actionSheet clickedButtonAtIndex:(NSInteger)buttonIndex
{
if(buttonIndex > 0) {
NSString *textValue = textField.text;
if ([textField.text length] <= 0)
{
UIAlertView *alert = [[UIAlertView alloc]initWithTitle: #"No Reference"
message: #"msg"
delegate: self
cancelButtonTitle:#"Cancel"
otherButtonTitles:nil,nil];
[alert show];
}
else{
CalculatorData *calcData = [self getCalcData];
calcData.dataKey = textValue;
if([database saveCalculatorData:(CalculatorData *)calcData tableName:[database Table]]){
[Utils showAlert:RECORD_SAVED];
}
}
}
}

Answer 1

What you can do is just find the instance of the textField of the alertView with below code
UITextField *alertTextField = (UITextField*)[alertView viewWithTag:REFERENCE_FIELD];
And then just put the code to show it's color to red with this code
[alertTextField setBackgroundColor:[UIColor redColor]];
May this will solve your problem :)

Answer 2

Did you try this?
textField.textColor = [UIColor redColor];

Answer 3

Try this:
- (BOOL) alertViewShouldEnableFirstOtherButton:(UIAlertView *)alertView
{
UITextField *textField1 = [alertView textFieldAtIndex:0];
[textField1 setDelegate:self];
NSString *inputText = [[alertView textFieldAtIndex:0]text];
if ([inputText length] == 7) // If it's 7 chars long, enable the button.
{
NSCharacterSet * set = [[NSCharacterSet characterSetWithCharactersInString:#"0123456789"] invertedSet]; // Only allow numbers
if ([inputText rangeOfCharacterFromSet:set].location != NSNotFound) { //Not a Number?
//show alert view here
textField1.backgroundColor = [UIColor redColor];
alertView.message = #"Only enter numbers please!";
return NO;
}
alertView.message = #"Fill in your number:";
return YES;
} else {
alertView.message = #"Fill in your number:";
textField1.backgroundColor = [UIColor clearColor];
return NO;
}
}
You can adapt it to your needs